In conventional communication systems, a communication terminal is connected to different external communication devices through separate I/O ports or connectors. In high-security military applications, a secure voice and data terminal (SVDT) has heretofore used discrete interface sections to interface with external communication devices for audio (analog) signals and for digital signals separately. Voice and/or data signals are processed digitally in the SVDT through a processor subsystem upon input from, or for output to, a digital I/O interface section connected to an external digital device for digital transmission, and to an analog I/O interface section connected to an external analog device for radio transmission.
The current SVDT system has the problem that the separate analog and digital I/O interface sections require separate installation within or outside of the terminal, thereby requiring considerable space to accommodate the interconnected parts. Moreover, when protective filter or isolator circuits for electromagnetic interference (EMI) and electromagnetic pulse transients (EMP) are provided between each interface section and the SVDT processor subsystem on one side, and the external device on the other side, the number of EMI and EMP circuits are multiplied.